The present invention generally relates to cooling systems for electrical and electronic components and subsystems, and more particularly to air cooling of electrical and electronic components.
Enclosures for containing and supporting electrical and electronic components are designed to meet various operating requirements. While maintaining the components inside relatively free from excessive shock, vibration and dust the enclosure needs to provide a system that cools or draws heat generated from the components. One way to cool the components is to provide a cooling airflow through the enclosure in order to remove heat that is generated by operating components.
As the packing density of electronic components increases in response to demands for higher performance systems, more printed circuit boards are being mounted closer together. The proximity of the boards greatly increases the airflow impedance and decreases the allowable maximum component height on each board. This creates difficult cooling problems such as hot spots and dead zones on the boards, and this is additionally complicated by the increased power requirement for today""s high-speed integrated circuits. These high-power, high-speed circuits not only require large volumes of airflow for cooling but also require very small enclosure openings to contain electromagnetic radiation.
The tangential, unidirectional nature of the airflow cooling methods causes multiple components to be cooled in series. Consequently, the downstream components are cooled by preheated air and thus are cooled by lesser amounts than are upstream components. Using a high airflow rate and heat sinks with large surface areas reduce the impact of this drawback. Fan modules that provide the high airflow rate are usually mounted on the back of the enclosure. The enclosure is typically designed with an air plenum that draws air through individual internal components via the fans of the airflow cooling system. An example of air volume flow rates for microprocessors in an electronic system is in the range of about 2.5 to 5 liters/second with a velocity of about 2 to 3 meters/second. Large multiple processor systems and large multiple disk drive systems used in dedicated computer rooms can be cooled by moving air at high mass flow rates with the resulting acoustic noise generally having to be tolerated. On the other hand, multiple processor and multiple disk systems used in office environments must meet more stringent acoustic emission guidelines and regulations as well as customer/user requirements. In these cases, cooling the systems by increasing the air mass flow rates in the traditional fashion is not a practical option.
It will be appreciated that there is a need for a system and an apparatus for effectively cooling the heat dissipating components of an electronic system without increasing the system""s enclosure size and cost. A system and an apparatus that address the aforementioned problems, as well as other related problems, are therefore desirable.
The present invention is directed to addressing the above and other needs in connection with cooling the increasing number of electrical and electronic components that are incorporated in enclosures that remain relatively constant in size. In addition, a single cooling apparatus of the present invention simultaneously provides different levels of cooling in response to the individual cooling needs of the various electronic components.
According to one aspect of the invention, a method for air cooling an electronic system disposed within an enclosure is disclosed. The electronic system to be cooled includes a plurality of electronic components and a blower arrangement coupled to a plenum. The method includes configuring the plenum to have at least one inlet and a plurality of outlets, wherein a first plenum outlet has a smaller outlet size than a second plenum outlet. At least two air ducts are coupled to the plenum outlets such that a first one of the air ducts is coupled to the first plenum outlet and a second one of the air ducts is coupled to the second plenum outlet. The first one of the air ducts produces a greater rate of airflow than the second one of the air ducts. The first one of air ducts is directed to a first set of electronic components and while the second one of the air ducts is directed to a second set of electronic components, wherein the first set of electronic components dissipate more heat than the second set of electronic components.
According to another aspect of the invention, an electronic system within an enclosure includes a cooling arrangement that cools a plurality of electronic components and a plenum. The plenum has an inlet and a plurality of outlets with the inlet receiving air from outside the enclosure. A rate of airflow at the respective plenum outlets varies as a function of a static air pressure behind the plenum outlets and a shape of the respective outlets, the static air pressure being a function of the shape of a cavity within the plenum. The system also includes a plurality of air ducts respectively coupled to the plurality of plenum outlets, with each air duct having a length and an outlet characterized by an outlet size. A first one of the air ducts has an outlet that is disposed proximate a first subset of the electronic components and a second one of the air ducts has an outlet that is disposed proximate a second subset of the electronic components. The electronic system further includes a blower arrangement disposed within the enclosure that draws external air and blows the air into the plenum.
It will be appreciated that various other embodiments are set forth in the Detailed Description and Claims that follow.